1. Field of the Invention
The present invention relates to the field of automated registration systems for use in continuous-web processes. More particularly, the invention relates to an automated method for applying a registered pattern to a web of material, wherein the pattern is registered relative to a previous pattern and tracks an irregular path of the web.
2. Description of the Prior Art
It is known in a variety of industries to implement a manufacturing technique that involves placing a series of parts or patterns on a continuous web of material. This technique may be used, for example, to manufacture flexible circuit boards wherein the web is a flexible substrate material and a series of circuits are printed on the substrate. When the parts are positioned at specific locations relative to each other, or relative to a determined feature, the parts are said to be produced “register” or “in registration.” The most common type of registration, known as “X registration,” is in the direction of movement of the web, sometimes referred to as the “machine” direction, which movement is along a longitudinal or X axis of the web, as shown in FIG. 1. FIG. 2 illustrates patterns that are printed on a web in X registration. Solutions for accomplishing X registration are well known in the art and include, for example, mechanical methods such as tractor feeds and optical methods such as fiber-optic sensors or imaging systems.
In some cases, it is required that the registration be in the machine direction as well as the orthogonal, or transverse, direction. Further, it may also be required that the patterns be aligned rotationally (wherein an angle of rotation is commonly denoted by the symbol Θ). Transverse registration, also referred to as XY registration, and rotational registration, also referred to as XYΘ registration, are well-known in the art and are implemented in various industries. FIG. 3 illustrates patterns that are in XY registration, that is, the position of each pattern is varied relative to a position of a previous pattern along both a longitudinal (X) axis and a transverse (Y) axis. FIG. 4 illustrates patterns that are in XYΘ registration, that is, the position of each pattern is not only varied relative to a position of a previous pattern along the X axis and the Y axis, but also is rotated relative to the previous pattern. XYΘ registration is known in the art and is described, for example, in U.S. Pat. Nos. 5,644,979, 5,212,647, 4,555,968 and 4,697,485.
Unfortunately, prior art methods of applying XY and XYΘ registration suffer from various problems and limitations. Webs, for example, often do not follow a straight path but are arbitrarily curved, in which case the web will tend to one side or the other during the manufacturing process. Eventually, a path followed by the parts will diverge from a path followed by the web such that the parts cannot be completely contained by the web, as illustrated in FIG. 5.
Accordingly, there is a need for an improved method of applying a series of registered patterns to a continuous web of material that follows an irregular path that overcomes the problems and limitations of the prior art.